This application relates to magnetic disc drives and more particularly to the protection of thin film sensors, such as magnetoresistive head structures, from damage caused by damaging electrical transients, such as electrostatic discharge.
Disc drives are data storage devices that store digital data in magnetic form on a storage medium on a rotating information storage disc. Modern disc drives include one or more rigid discs that are coated with a medium that can be magnetized. These discs are mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks. Each of the concentric tracks is generally divided into a plurality of separately addressable data sectors. The read/write transducer, e.g., a magnetoresistive read/write head, is used to transfer data between a desired track and an external environment. During a write operation, data is written onto the disc track and during a read operation the head senses the data previously written on the disc track and transfers the information to the external environment. Critical to both of these operations is the accurate locating of the head over the center of the desired track, by a function referred to as servoing.
The heads are mounted via a suspension on flexures at the ends of actuator arms that project radially outward from the actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
Trends in the disc drive industry have required disc drive manufacturers to provide drives with increased areal densities. In order to meet this growing demand, much advancement in read/write head technology have been implemented. One such advancement was moving from an inductive head design to a magnetoresistive (MR) head structure due to the many advantages a MR head offers.
Although there are many benefits with MR technology, there is a distinct problem associated with the improved sensitivity. An MR head is 100 times more sensitive to electrostatic discharge (ESD) than the older inductive heads. Furthermore, since their introduction, MR head structures have shrunk in order to meet growing areal density demands, making the MR heads even more sensitive to ESD. The latest MR head technology, called GMR (Giant Magnetoresistive), is sensitive to ESD levels as low as 3 volts, and below.
ESD is an uncontrolled static charge transfer from one object to another. In MR heads, ESD occurs when there is a buildup of charge on various elements of the head or other elements in the read/write assembly that are in electrical contact with the MR element of the head, and the head is momentarily shorted to ground. The charge runs through the MR element into ground, thus creating an ESD pulse that is potentially damaging for the MR element.
ESD is only a minor concern in a completed, and operational disk drive. Once in a completed disc drive, the MR elements on the heads are typically protected. The drive case shields the heads from particulate contamination, human contact and other adverse elements that could cause an ESD event.
However, ESD presents a major problem during manufacture, installation and handling of the head and drive, because drive-level ESD protective measures are not yet in place. Therefore, ESD from human or equipment contact and electric fields can cause damage to the MR structures in the head, thereby reducing effect yield and raising costs.
Because of this constant potential damage to the MR head from ESD during manufacturing and handling, it is desirable to protect the MR head from ESD damage. One such method of MR head protection is by shorting together some or all of the electrical circuitry that connects to the MR head, a process generally known as shunting. By shorting the circuitry leading to the MR head, a low resistance path to ground exists. Therefore, the ESD pulse is directed through the short and bypasses the MR structure, thereby protecting the head.
However, when the MR head is required to function, for example during testing of the head, the electrical shunt will also short out any electrical input to or output from the head. Therefore, the shunt must be removed from the head during electrical testing. After testing is complete, there is often additional processing and handling that must occur prior to final installation. As such, with the shunt removed for testing, the head is again vulnerable to damage from ESD during these additional processing and handling steps. Therefore, it is desirable to reinstall a shunt, or xe2x80x9cre-shuntxe2x80x9d the MR circuit after testing. Many shunting methods and devices do not allow for the easy re-shunting of the head after testing.
Therefore, there is a need in the relevant art to overcome the shortcomings of the traditional ESD protection mechanisms.
Against this backdrop, the invention has been developed. The invention includes an apparatus and method for shunting a thin film sensor, for example, shunting an MR head.
In accordance with one preferred embodiment, the invention is implemented as a method for protecting a thin film sensor such as a magnetoresistive element from damaging electrical transients, such as electrostatic discharge. The method includes providing a thin film sensor assembly such as a magnetoresistive head including the sensor in electrical contact with a first and a second electrical contacts. A shunting structure is deposited between and in electrical communication with the first and second electrical contacts such that the shunting structure as deposited is a high resistance path between the first and second electrical contacts and does not electrically short the first and second electrical contacts. Heat treating the shunting structure then forms a low resistance path between the first and second electrical contacts to provide protection of the thin film sensor assembly from damaging electrical transients.
The invention can be implemented in accordance with another preferred embodiment as an assembly for providing electrical protection to a thin film sensor such as a magnetoresistive element. The assembly includes a thin film sensor assembly including the thin film sensor, and first and second electrical contacts in electrical communication with the sensor. The assembly further includes a shunting structure deposited between and in electrical communication with the first and second electrical contacts. The shunting structure as initially deposited is a high resistance path between the first and second electrical contacts and does not electrically short the first and second electrical contacts. When the shunting structure is heat treated, the shunting structure thereafter becomes a low resistance path between the first and second electrical contacts to provide protection of the thin film sensor assembly from damaging electrical transients.